1. Field of the Invention
The present invention lies in the area of printed circuit board (PCB) assembly.
2. Description of the Related Art
The assembly of electronic components containing a printed circuit board sometimes requires that the PCB be precisely positioned (xc2x10.001 inches or so) on a mounting plate (sometimes called a carrier plate). Alternately, the PCB may need to be positioned precisely on a heat sink. Indeed, positioning needs to be especially precise when assembling components in RF applications, where correct performance of the final assembly depends on precise positioning of the PCB on the mounting plate.
The prior art contains a number of different methods for precise positioning of the PCB relative to the mounting plate. The simplest method is for the assembly operator to manually align the PCB using visual inspection. Although acceptable to a degree, visual inspection is naturally subject to human errors. In addition, visual inspection may require additional time during assembly in order to have an acceptable degree of alignment.
Another technique is to insert dowel pins into the mounting plate, where the pins match corresponding holes on the PCB. Closely related is the technique of inserting alignment blocks into features in the mounting plate. Both of these techniques however, add the required step of adding pins or blocks or similar fixtures to the mounting plate that serve no useful purpose other than PCB alignment during the assembly process. In addition, holes will need to be cut in the PCB solely for the purpose of aligning the components. These prior art techniques add cost to the manufacturing of the mounting plate or the PCB.
By contrast, the present invention solves these alignment problems by taking advantage of features already existing on both the PCB and the mounting plate. The described mechanism manages to utilize cutouts already found on the PCB.
Briefly described, the invention is an apparatus and method for precisely aligning a printed circuit board (PCB) to a mounting plate onto which the PCB will be fastened by taking advantage of component cutouts already cut into both the PCB and the mounting plate. The mechanism consists of two major plates, one mounted onto the other by means of an eccentric cam. The larger top plate contains holding pins for the mounting plate as well as a notched center locator and two edge locators, all of which project through both cutouts on the PCB and the mounting plate. The mounting plate and PCB are moved into position by means of a pressure plate mounted onto the top plate by means of an eccentric cam. The pressure plate contains one set of leaf springs for moving the PCB and a pair of spring plungers for moving the mounting plate.
The operator begins by placing the top plate on top of both the PCB and the mounting plate and wiggles the center locator until it matches up with a notch cut between two cutouts that exist both on the PCB and the mounting plate. The operator then fits two edge locators into the two cutouts, and fits the pressure plate so that one set of springs contacts the PCB while the other contacts the mounting plate. Once the PCB, the mounting plate and the top plate are in place, the operator rotates the eccentric cam, pushing both PCB and mounting plate along the cutouts and back towards the operator until the edge locators reach the end of the cutout, thereby aligning the respective plates.